Alkylation of alkyl sulfates



May 6, 1969 H. E. MASSA ALKYLATION OF ALKYL SULFATES Sheet Filed Oct. 12. 1965 May 6, 1969 H. E. MASSA ALKYLATIVON OF' ALKYL SULFATES 3 ofe Sheet Filed Oct. 12, 1965 INVENTOR. Ha/jy E Massa BY l 55 nrrod Sheet INVENTOR.

H. E. MASSA ALKYLATION OF ALKYL SULFATES .mmf

May 6, 1969 Filed oct. 12, 196s Har/y i. Mad BY rma/vens.

May 6, 1969 H. E. MASSA ALKYLATION 0F ALKYL SULFATES Sheet Filed Oct. 12, 1965 NvENToR /V//jj/ .5. Mdf

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Y f l AnjoRNExs May 6, 1969 INVENTOR Har/y E.` Ma@ May 6, 1969 H. E. MASSA ALKYLATION OF' ALKYL SULFATES rSheet Filed Oct. l2, 1965 INVENTOR ATTORNEYS #amy P045@ E. /Wa

Salad/'afar Ha/y /97 United States Patent O U.S. Cl. 260--683.61 8 Claims ABSTRACT F THE DISCLOSURE A sulphuric acid recovery process used in conjunction with sulphuric acid alkylation for the recovery and reuse of spent alkylation acid. The sulphuric acid in the spent alkylation acid is reacted with olefins in a continuous process to produce dialkyl sulfates. Dividing the reaction product of the sulphuric acid and olefin into a relatively lighter phase having therein normal paraflinic hydrocarbons, a quantity of alkyl esters and probably excess unreacted olefin and a relatively heavier phase comprising dialkyl esters, monoalkyl esters, acid, water and acid soluble contaminants. Conserving the alkyl ester values and any olefin values of said light phase for return to the alkylation reaction zone.

This invention relates to a sulfuric acid recovery process used in conjunction with sulfuric alkylation for the recovery and reuse of spent alkylation acid and refers more particularly to methods employed in and with said sulfuric acid recovery process wherein H2804 in the spent acid is reacted with olefin in a continuous process to produce dialkyl sulfates. The invention further relates to method improvements in and cooperating between a sulfuric acid alkylation process wherein olefinic feed stocks are alkylated with isoparaflins in the presence of sulfuric acid catalyst wherein the catalyst is continuously revivified in an integrated system. Still further, the process relates to improvements and modifications within and among the parts and process steps of a sulfuric acid recovery process wherein, in conjunction with a sulfuric acid alkylation process wherein isoparafiinic hydrocarbons are alkylated with olefinic hydrocarbons in the presence of a sulfuric acid catalyst, the H2804 in the spent acid is reacted with olefin, separated from catalyst impurities and returned to the alkylation reaction system.

Isoparaffinic hydrocarbons such as isobutane, isopentane and the like may be reacted with olefinic hydrocarbons in the presence of catalysts to produced alkylated isoparafiinc hydrocarbons. -Isobutane may be reacted with butylene to produce iso-octane, the iso-octane being a typical hydrocarbon present in the desired motor fuel. The reaction is a condensation reaction which is exothermic and takes place in the presence of catalysts such as sulfuric acid. An excess of the isoparaffinic reactant must be maintained during the reaction in order to minimize the polymerization of the olefinic reactant. Olefins tend to polymerize more readily than to condense with the isoparaflinc hydrocarbons. The polymerization is reduced by conducting the reaction at reduced temperatures.

In the course of alkylation of isoparaffins with Olefins, sulfuric acid catalyst becomes contaminated with a polymeric organic contaminant and with water, both of which impair the catalyst activity. This contaminant appears to be a complex mixture of reaction products from polymerization and acid reaction such as sulfation and sulfonation. Its exact composition is unknown and varies with types of feed stocks and reaction conditions. This material is variously referred to as acid oil, polymeric oil, acid-soluble sludge or as acid soluble complex.

3,442,972 Patented May 6, 1969 ice This polymeric organic contaminant is soluble in or chemically bound by strong sulfuric acid but is insoluble in acid diluted to less than about 50 percent acid by weight with water.

In accordance with the usual procedures of the prior art, this organic polymeric contaminant is eliminated from the alkylation system by withdrawing acid of about 88 to 92 percent concentration as spent acid from the alkylation system at the rate of about 0.3 to 1.2 pounds per gallon of alklyate produced and replenishing the systern with fresh acid of about 98 to 100 percent H2804. Since the polymeric organic contaminant amounts to only about 3 to 8 percent of the spent acid, a large amount of acid must be disposed of in order to eliminate a relatively small amount of the polymeric organic contaminant from the system. It has previously been attempted to separate the polymeric organic contaminant from the acid by various methods unsuccessfully, including the use of solvent extraction, contacting with a solid absorbent, crystallization, vacuum disillation, and treatment with various chemicals.

Acid recovery processes have been projected wherein sulfuric acid from an alkylation zone is recovered by reacting a portion thereof with an olefin forming alkyl esters, with the resulting absorption product contacted with a light hydrocarbon at a relatively low temperature effecting extraction of polymeric organic contaminants from a residue comprising alkyl esters and remaining unreacted sulfuric acid.

It appears that the reaction of olefin with the acid changes the characteristics of the reaction mixture so that the contaminants are less tightly held by the reaction products. If approximately 2 mols of olefin per mol of acid are absorbed by the acid, it appears that substantially all of the acid is converted to alkyl sulfates and predominantly the dialkyl sulfates.

In the catalytic al-kylation of isoparaffins with olefinic material, a large excess of isoparafiin is provided in the reaction zone to direct the reaction toward the production of the most valuable isomers for use in aviation or automotive fuels. This is generally accomplished through recovering by fractionation and recycling sufiicient isoparaffin to provide 50 to 80 volume percent of the hydrocarbon in the reaction mixture. Isobutane is generally used as the isoparaffin for the manufacture of aviation or motor fuel although other isoparaffins, for example isopentane, may be employed.

The volume percentage of ctalyst phase in the total mixture reactor is generally held within the range of 30 to 70 percent. Catalyst strength in the alkylation zone is preferably maintained at least about percent sulfuric acid strength.

In accordance with the process of this disclosure, the olefinic material reacted with an isoparafiin in the alkylation zone comprises a mixture of olefins and alkyl esters.

Alkyl esters are produced by reaction of alkylation acid with olefin in a separate absorption step. Olefins, for example, propylene, butylenes or mixtures of olefin, may be reacted with sulfuric acid to form alkyl esters. The reaction mixture formed upon contacting a hydrocarbon stream containing mixed olefns with sulfuric acid comprises a complex mixture of monoand diesters containing straight chain and branched chains.

In maintaining catalyst strength in sulfuric acid catalyzed alkylation, it is generally necessary to withdraw acid at a rate of about 0.6 to 1.5 pounds per gallon of alkylate produced. The acid withdrawn may have a composition, for example, of 90.0 weight percent H2804, 3.0 weight percent water and 4.5 weight percent polymeric organic' contaminants. The purpose of withdrawing the spent acid is to reject the water and contaminants, and this stream is reprocessed to recover the remaining acid.

In accordance with the disclosure of this invention, 50 to 95 percent of the sulfuric acid contained in spent acid is recovered in the form of dialkyl sulfates. Upon separation and alkylation of this dialkyl sulfate, sulfuric acid of 100 percent strength is liberated in the reaction zone so that the make-up acid rate may lbe reduced to about to 50 percent of that otherwise necessary.

Olefin streams from a wider variety of sources than are suitable for procedures of the prior art may be used for absorption in spent alkylation catalyst due to the fact that these streams are processed prior to alkylation. Thus, streams containing such materials as ethylene and butadiene which are generally considered undesirable for inclusion in alkylation feeds may advantageously be fed to absorption for removal and rejection of the undesirable components.

An object of this invention is to provide an improved alkylation process.

Another object of the invention is to recover spent sulfuric acid alkylation catalyst for reuse in alkylation.

Another object of the invention is to provide a sulfuric acid alkylation process with a linked sulfuric acid recovery process wherein propylene and butylene feed streams may be charged through the absorption and the alkylation step respectively, such that the spent acid from the butylene alkylation may be recovered and reintroduced in the alkylation zone in the form of dipropyl sulfate.

Another object of the invention is to enable the optimum sulfuric acid catalyst composition for a particular application to be achieved and maintained in a sulfuric acid alkylation process by the suitable addition of the desired amount of dialkyl esters to the alkylation reactors.

Another object of the invention is to provide a sulfuric acid alkylation recovery process wherein savings in acid and decreased acid consumption are achieved by virtue of the provision of an improved sulfuric acid recovery process therewith.

Another object of the invention is to provide a sulfuric acid alkylation process with an associated sulfuric acid recovery process wherein elimination of inerts (propane and n-butane) may be selectively provided associated with the absorption step or section of the acid recovery process rather than by fractionation in the alkylation section with resultant higher isobutane concentration in the alkylation reactor.

Another object of the invention is to provide a sulfuric acid alkylation process with the sulfuric acid recovery process associated therewith resulting in improved quality of alkylate product because of improved conditions in the alkylation reaction step.

Another object of the invention is to provide an alkylation system and process and associated sulfuric acid recovery process wherein there is a relatively lower water content of system alkylation acid, the bulk of the acid charged to the alkylation section in the form of dialkyl sulfates being essentially free of water.

Another object of the invention is to provide a sulfuric acid alkylation process and associated acid recovery process wherein there is a large reduction in the amount of fresh acid and spent acid to be handled at the alkylation unit for transportation by truck and tank cars.

Another object of the invention is to provide such alkylation system and acid recovery system therewith wherein there is a greater toleration for impurities, ethylene and butadiene in the feed streams, or reduced treating requirements.

Another object of the invention is to provide an absorption step for an acid recovery system associated with a sulfuric acid alkylation system wherein a high percentage or substantially all of the olen is removed from the charge stock, wherein a high percentage of the available acid in the charge spent acid to the absorption step is converted to a dialkyl sulfate.

Another object of the invention is to provide an improvement in the absorption step of an acid recovery system coupled with a sulfuric acid alkylation system wherein, in the absorption step where used acid from the acid settler of the alkylation system is reacted with a feed stream containing both normal and olefinic hydrocarbons to produce dialkyl sulfate and the absorption efliuent is divided into an acid-rich heavy phase and a hydrocarbonrich light phase, the latter is taken directly to the alkylation reaction zone for recovery of any entrained alkyl sulfates and reaction of any olefin present in the stream.

Another object of the invention is to provide an absorption step for a sulfuric acid recovery process and a sulfuric acid alkylation process wherein olefin-containing hydrocarbons are reacted with spent alkylation acid to produce a preponderance of dialkyl sulfates, the absorption stage effluent separated into a light phase containing normal parafnic hydrocarbons, any unreacted oletinic hydrocarbons and dissolved alkyl sulfates and a relatively heavy phase comprising any unreacted acid, water alkyl sulfates and acid soluble contaminants, the light phase passed to the alkylation step from the absorption step whereby the alkyl sulfates therein may be recovered in the alkylation reaction zone. Any olefins remaining in the light phase from the absorber are also recovered in the alkylation step, thus affording complete utilization of the olens. In this connection, the absorption step may 'be made more efiicient for the production of alkyl sulfates as the complete utilization of the olefin is not necessarily required in the absorption step.

Another object of the invention is to provide such an absorption step in a sulfuric acid recovery process associated with a sulfuric acid alkylation process wherein all components of the various streams in the absorption step may be retained at all times in the liquid phase, the state in which they are normally utilized. Further, the paratlinic hydrocarbons from the light phase from the absorption step and system may be recovered, alternatively, prior to the return to the alkylation zone with a minimum of effort and apparatus or, without further or additional processing, from the alkylation step in a form most convenient for further use.

Another object of the invention is to provide a sulfuric acid recovery process for sulfuric acid alkylation wherein the acid recovery process is readily incorporated into a conventional alkylation system with a minimum number of tie-in points and a minimum disturbance in design and operation of the alkylation section of the plant. A portion of the refrigeration duty may be shifted from the alkylation reactors to the recovery unit, but with the exception of some additional mechanical and atmospheric heat load, the total refrigeration duty remains essentially the same.

Another object of the invention is to provide improvements in a sulfuric acid recovery process for sulfuric acid alkylation, which acid recovery process normally involves (1) an absorption step, wherein used alkylation acid is reacted with an olefin bearing feed stream to produce dialkyl sulfates and a phase separation is achieved dividing excess light hydrocarbons and some entrained alkyl sulfate from the alkyl sulfate and polymeric contaminant phase, (2) an extraction phase wherein light hydrocarbons are employed to extract the alkyl sulfates from the polymeric contaminant phase and (3) a further optional acid treating step scavenging traces of polymer from the alkyl sulfate extract phase, the improvements comprising linking the absorption step with the extraction step, acid treating step or the alkylation step in such manner as to effect complete recovery of unreacted olens and alkyl sulfates previously sacrificed.

Another object of the invention is to produce and effect an absolutely concrete, nonhypothetical, commercial system adapted to competitively function in the current art and at considerable advantage to existing alkylation and acid recovery systems; hitherto general and vague concepts of sulfuric acid recovery long known to the art but unrealizable in effective efficient commercial practice being so embodied in process stages and apparatus arrays that the necessary efficiency and cooperation between the specific steps and components of the alkylation system and the acid recovery system are provided, all stages integrated into an over-all cooperating, functional system whereby a long sought after but unrealized ideal is achieved.

Another object of the invention is to provide a sulfuric acid recovery process for use with a sulfuric acid alkylation process wherein the former imparts a strong stabilizing effect to the latter, allowing quick recovery from and minimizing the effects of upsets.

Another object of the invention is to provide an acid recovery process for use in sulfuric acid alkylation wherein essentially pure, high quality dialkyl sulfates are produced which, on return to the alkylation reaction, react with isobutane in the presence of the alkylation catalyst, releasing sulfuric acid, fortifying the alkylation catalyst, reducing the requirements of fresh acid make-up, maintaining eifective catalyst strength and producing high quality alkylate, the latter having increased octane number and a reduction in ASTM end point.

Another object of the invention is to provide an acid recovery process for sulfuric acid alkylation wherein an olefin-containing hydrocarbon feed stream is reacted with used acid from the alkylation section in an absorption step, any olefin present in said feed stream being recovered and reacted either there or in the alkylation zone, thus insuring no waste of olefins fed to the alkylation plant and acid recovery system.

Another object of the invention is to provide an olefinsulfuric acid absorption step for use in a sulfuric acid recovery process operated in conjunction with a sulfuric acid alkylation system wherein there is production in the absorption step of a maximum quantity of dialkyl sulfates as well as complete conservation and utilization of same in alkylation.

Other and further objects of the invention will appear in the course of the following description thereof.

In the drawings, which form a part of the instant specification and are to be read in conjunction therewith, embodiments of the invention are shown and, in the various views, like numerals are employed to indicate like parts.

FIG. 1a is a schematic fiow diagram of a sulfuric acid alkylation process wherein a typical efficient alkylation reaction is illustrated utilizing indirect heat exchange of the reaction effected by effluent refrigeration. The flow lines tying the alkylation system of FIG. la to the sulfuric acid recovery system of FIG. 1b are at the right side of the figure.

FIG. lb shows a first form of acid recovery system, connecting with the alkylation system of FIG. 1a through iiow lines at the left side of the figure.

FIG. 2 is a view of a second form of acid recovery system for sulfuric acid alkylation, differing from that of FIG. 1b in that a normal paraffin hydrocarbon removal stage is shown applied to the acid recovery absorption system light phase prior to return to the alkylation step and the acid treating step of FIG. 2 removed.

FIG. 3 is a schematic fiow diagram of a sulfuric acid recovery system analogous to FIGS. lb and 2, but differing from the latter two views in having but a single stage absorption section with the light phase from the absorption step being utilized in the same manner as shown in FIG. lb.

FIG. 4 is a simplified block diagram of the alkylation system-acid recovery system hook-up of the previous figures.

FIG. 5 is a side-sectional view of a vertically oriented liquid contact apparatus with suitable flow lines attached whereby same may be utilized as an absorber vessel in the absorption step of the instant invention (multistage countercurrent).

FIG. 6 is a View taken along the line 6 6 of FIG. 5 in the direction of the arrows.

FIG. 7 is a schematic flow diagram of a time tank system substitutable as the absorber in the absorption step of the instant invention.

With respect to the drawings, FIG. 4 will be first described to give a generalized picture of the sulfuric acid alkylation system in simplified terms and the same with respect to the acid recovery system and the relationship of these two to one another.

Isobutane in line 10 and from recycle line 20 is mixed with olefins, optionally butylenes, in line 11 and the mixture passed to alkylation reactor 12. Sulfuric acid catalyst or the equivalent thereof is introduced into reactor 12 from line 13. isobutane, olefins and acid are reacted therein which is withdrawn and passed through line 15 to acid settler 16. Acid catalyst is recycled via line 13. Fresh acid may be separately added to the alkylation system through line 14 in required amounts.

The hydrocarbon phase from settler 16 is passed through line 17 to conventional neutralization and fractionation steps schematically indicated at 18. Isobutane withdrawn from fractionation through line 19 is recycled via line 20 to the alkylation zone. Makeup isobutane is added to the system through line 10. Alkylate product leaves the system through line 21.

A portion of the recycle acid in line 13 is withdrawn through line 25 and introduced to an absorption step schematically shown at 26. A stream comprising parafnic and olefinic hydrocarbons (typically predominantly propylene and propane) is introduced into step 26 through line 27. In step 26, the olefins react with used alkylation acid forming alkyl sulfates.

Two distinct and separable phases, one relatively lighter and the other relatively heavier, result from the absorption reaction. The lighter of these, discharged through line 28, typically includes paraffinic and any unreacted olefnic hydrocarbon and alkyl sulfates dissolved therein. In order to conserve such olefinic hydrocarbon as may be present and the sulfates dissolved in the light phase, the latter is passed to the alkylation zone, either directly as seen at 28, or indirectly as will be shown in and described with respect to the other figures of this specification. The relatively heavier phase, comprising alkyl esters, water polymeric contaminants and any remaining unreacted acid is withdrawn through line 30.

The absorption step is desirably maintained within a temperature range of about 10 to 70 F. Since the absorption reaction is markedly exothermic, it is necessary to cool the absorption step to maintain the temperature Within the desired range. Cooling of the absorption step may be effected by cooling the feed streams thereto, or preferably by cooling the materials Within the absorption step, the latter typically by indirect heat exchange methods. Coolant may be supplied by a separate refrigeration system or may be effected with a process stream.

The absorption step heavy phase is passed through line 30 to an extraction step diagrammatically indicated at 37. Hydrocarbon solvent (preferably isobutane from fractionation 18) is cooled to a temperature in cooler 35 and introduced to step 37 through line 38. The absorption heavy phase and solvent are contacted in step 37 effecting extraction of dialkyl sulfates from the heavier absorption phase. Said alkyl ester extract is withdrawn through line 40 and passed to alkylation reactor 12. The extract is made up of solvent and esters together with traces of polymeric contaminants. Rafinate comprising alkyl esters, acid, water and dissolved polymeric contaminants is withdrawn through line 41.

Extraction step 37 may be effected in contacting equipment known in the art, for example, mixer-settlers, centrifugal contactors or countercurrent towers. In a countercurrent tower, for example, the absorption heavy phase is introduced at the top and raffinate is discharged from the tower bottom. The hydrocarbon solvent is introduced at the bottom and extract mixture comprising the dialkyl sulfates dissolved in the solvent is removed at the top.

The temperature of the extraction zone may be controlled by cooling the hydrocarbon solvent passed to the bottom of the extractor.

Various light hydrocarbon solvents may be employed in the extraction step of this invention, isobutane being preferred because of its utilization in the alkylation reaction. Usually 3 to l0 volumes of solvent per volume of absorption heavy phase, or less, are sufficient.

In general, to obtain maximum recovery of spent alkylation acid, and also to obtain efficient use of the olefin charged to the absorption step, the maximum amount of olefin possible should be reacted with spent alkylation acid. Theoretically, this corresponds to 2 mols of olefin per mol of available sulfuric acid, giving 100 percent conversion of the acid to dialkyl sulfated.

For the purposes of my invention, olefin-based alkylatable material includes olefins, alkyl esters and their mixtures. Such esters are primarily produced by reaction of alkylation acid with olefin in the absorption step.

More particularly, the over-all process may be described as:

(l) Absorption of olefin (typically propylene) in used alkylation acid, with separation of a light hydrocarbon phase containing parains, such as propane, any unreacted olefin and dissolved alkyl sulfates.

(2) Extraction of dialkyl sulfates from the heavy phase of the absorption step, preferably employing fractionation isobutane from an alkylation unit, with elimination of water and polymeric contaminants originally present in the used alkylation acid.

(3) Optional treatment of the isobutane-alkyl sulfate extract with a small amount of spent alkylation acid to remove any polymeric contaminants not removed in the extraction step.

(4) Charging of the acid treated isobutane-alkyl sulfate extract to an alkylation unit for generation of 100 percent sulfuric acid and alkylate from the alkyl sulfates and isobutane. (Fresh make-up acid would be added to the alkylation reactor equivalent to that lost in the raffnate in the extraction and acid treating steps which would represent the net acid consumption. Olefin feed stock would also be charged to the alkylation reactor.)

Sulfuric acid alkylation system Referring to FIG. la, therein is shown a quite standard sulfuric acid alkylation process, apparatus array and system wherein a circulating reaction vessel of the Stratco Contactor type is employed with indirect heat exchange by effluent refrigeration of the reaction zone. With the exception of the linkages to the acid recovery system, the combination of apparatus and the flow line linkages are quite conventional.

Contactor 50, here shown as horizontal, has a circulating tube 51 with an impeller 52 at one end thereof driven by power source 53. Tube bundle 54 extends from header 55 which is divided by plate 56. In vessel 50, olefinic hydrocarbons are alkylated with isoparafiinic hydrocarbons in the presence of sulfuric acid catalyst in conventional manner with the reaction effluent, comprising alkylate, excess isoparaffnic hydrocarbons, polymeric acid contaminants and the like being taken off overhead through line 57 to acid settler 58. The hydrocarbon phase of the reaction efiluent is taken off overhead from the settler through line 59 and passed to the input side of the tube bundle after back pressure valve 60. The latter maintains the reaction under liquid phase conditions and the cooling after expansion through such valve of the hydrocarbon phase of the reaction effluent, according to well-established practice in efliuent refrigeration, maintains the reaction zone temperature as desired. From the upper portion of header 55, line r61 carries the hydrocarbon phase eiiiuent, both liquid and vapor, to trap and flash drum 62. This vessel has a divider 63 centrally thereof which divides the liquid in the sides thereof but permits communication thereover for vapor phase from 'both sides of the trap.

Vapor overhead from trap 62, comprising light excess isoparainic hydrocarbons and normal parainic hydrocarbons are taken off through line 64, passing to compressing stage 65 and condenser 66 and thence via line 67 to accumulator 68. Liquid from accumulator 68 may pass through line 69 through valve 70 back to trap 62 or alternately bottoms liquid is taken off through line 71 via pump 72 through a heat exchange step at 73 to depropanizer tower 74. The overhead from tower 74 is taken off through line 75 through cooler 76 and to vessel 77. Overhead from vessel 77 goes out of the system through line 78 as propane with the bottoms fraction returned to tower 74 via line 79 and pump 80. Bottoms from tower 74 are returned via line 81 through heat exchange at 73 and through cooling step 82 and valve 83 to the bottoms of trap 62. Reboiling takes place via line 84 heated at 85.

The trap and flash drum -bottoms on the left-hand side of the trap and fiash drum in the view are linked with the acid recovery system to be described, but are returned and handled with respect to the alkylation reaction and associated systems via line 86, pump 87, valve 88 controlled by level control 89. Line 86 returns the trap bottoms, largely comprising unreacted isoparaflinic hydrocarbons, via input fitting 89, comprising a nozzle to a position interior of the circulating tube before impeller 52. On the right-hand side of barrier 63 in the view, trap bottoms are returned into the system via line 90 through pump 91 and valve 92, also controlled by level control 93. From valve 92, the trap bottoms are passed via line 93 through heat exchange at 94 to meet line 95 passing to a caustic wash step at 96 with a receiving vessel at 97. From vessel 97, recycle line 98 splits into line 99 out of the system and line 100 which, via pump 101 returns the caustic wash bottoms through the mixer 96. Fresh caustic is input to the system through line 102. Overhead from the caustic operation passes the alkylate through line 102 and mixing step 103 after input of fresh water at line 104 to vessel 105. Bottoms from vessel 105 go out of the system at line 106, with the overhead passed through line 107 and via heating step 108 to deisobutanizer tower 109. The overhead from tower 109 is taken off through line 110, condensed at 111 and passed to vessel 112. Liquid from vessel 112 passes via line 113 to fractionation recycle line 114 via heat exchange at 115 to join the butane butylene input feed through line 116 (or alternatively recycles to vessel 109). This olefinic input and the excess isoparaffinic hydrocarbons returned via line 114 go through heat exchange at 94 to a separation step at 117 and thence through line 118 to input fitting 120 opposite fitting 89 in front of impeller 52. Water goes out of the system from separator 117 through line 121. Part of the fractionation recycle may be diverted `to the acid recovery system through line 122 after heat exchange at 115, as will be later described. Reboiling in the deisobutanizer tower is seen at 123 with heat applied at 124. Bottoms from the deisobutanizer tower pass via line 125 to debutanizer tower. The overhead from the latter is taken off through line 126 through condensing at 127, accumulation at 128 and recycle for reboiling through line 129 through pump 130. Normal butane is removed from the system through line 131. Bottoms from debutanizer tower go out of the system through line 132 after condensation at 133 with reboiling of the lower fraction of the tower achieved at line 134 with heat applied at 135.

Fresh acid is supplied to the alkylation system of FIG. l through line 134, meeting acid recycle line 135 from settler 58 and passing through common line 136 into the circulating tube of the reactor. Line 137 splitting off from recycle line 135 carries used alkylation acid from acid settler 58 to the acid recovery system to be described. On the left side of `the flash drum 62, line 138 carries a bleed stream 9 of hydrocarbon bottoms from flash drum 62 to the acid recovery system for cooling while line 139 returns same from the acid recovery System.

Turning to FIG. 1b', therein is shown an acid recovery system utilizing a two-stage absorption phase with an extraction phase followed by an acid treatment step. Absorbers 1 and 2, seen at 140 and 141, are contactors of the type seen at 50 in FIG. la. Detailed disclosure of such is made in Putney 2,979,308, issued Apr. 11, 1961 entitled Apparatus for Controlling Temperature Change, etc. The extraction phase is preferably carried out in a rotating disc contacting vessel 142, and the acid treatment stage in a contactor of the type previously described at 143. Power means 140a, 141a and 143a drive the impellers in each of the respective contactors with power means 142a supplying drive for the RDC. Settling vessels are seen at 144 for the tirst stage absorber, 145 for the second stage absorber and 146 for the acid treater.

A preferably preponderantly propane-propylene feed is input to contactor 140 at the first absorption stage through line 147. This is mixed in vessel 140` with the bottoms from the second stage absorber settler vessel 145 passed therefrom via line 148. The eiuent of the No. 1 absorber is passed to settler 144 through line 146 and comprises primarily dialkyl sulfates, namely, dipropyl sulfate, perhaps a small percentage of monopropyl sulfate, preferably a minimum, excess normal paraflinic hydrocarbons of the propane level and an excess of olenic hydrocarbons. No excess acid, in effect, is found at this stage, sufiicient olefin being provided and sufficient mixing effected in the two absorbers that all H2504 in the input through line 148 to contactor 140 is reacted. There is a quantity of acid soluble polymeric contaminants and water in the settler 144 contents, as well.

The overhead from settler 144 is taken off through line 149 and passed to contactor 141 where it is met by an incoming stream of used alkylation acid via line 150. This material has come down into the acid recovery system via lines 151 and 1,52 through pump 153. Line 152 coming out of the alkylation system is line 137. The effluent from absorber No. 2, contactor 141, passes overhead through line 152 to settler No. 2 at 145. The bottoms from settler No. 1 at 144 are passed through line 155 over to the extraction phase of the acid recovery system. To sum up the functional side of the absorption system, the used acid coming down through lines 137-152 goes into the No. 2 absorber where it meets the overhead from the No. 1 settler 14'4. Thus the original propane propylene feed has already been diluted or depleted of a certain amount of olefin via what has been taken out in the No. 1 absorber. The reactor overhead from the No. 2 absorber 141 is thus acid rich and propylene poor. The bottoms from the No. 2 settler 145 have been stripped of excess normal propane, other light hydrocarbons and at least a slight excess of propylene (required to drive the absorption reaction to the dialkyl sulfate stage), these light components and some much smaller percentage of alkyl sulfates dissolved therein are taken off overhead from the No. 2 settler through line 156. Returning to the No. 2 settler, the bottoms therefrom, comprising acid rich and propylene poor absorption product, are passed via line 148 to absorber No. 1 at 140 Where the already partially sulfated acid is moved strongly to the dialkyl side by the impact of the new propane propylene feed input to the vessel through line 147. The overhead product through line 146 has a considerable excess of propylene and light hydrocarbon. The settler 1414 contents is stripped of the latter two through line 149 which passes to the No. 2 absorber 141. The ultimate absorption product, very preponderantly dialkyl sulfate, but also including any acid, water and acid soluble contaminants, is taken out line 155.

Indirect heat exchange of the absorption reactor steps at 140 and 141 is provided by flowing bottom hydrocarbons from flash drum 62 through line 138 to take-off lines 157 and 158 connecting to tube bundle headers b and 1|41b, respectively. After a heat exchange connection at 159, line 138a connects into return line 139 to tiash drum 62. Return lines 157a and 158a from headers 140b and 141b connect into line 138a to complete the circuit through the tube bundles of absorbers 1 and 2. The entire absorber-settler system is maintained under suicient pressure that all the reactants of the absorption step are maintained in liquid phase. The pressurization of this system is the reason for pump 153.

The reaction or absorption is exothermic, resulting in a rather high heat release at the point of reaction, thus cooling is required to maintain the reaction temperature at the desired level of approximately 30 F. A significant portion of the dialkyl sulfate goes into solution in the hydrocarbon phase. Thus, after the reaction mix is withdrawn from the contactor and separated, a portion of the dialkyl sulfate leaves the separating vessel with the hydrocarbon phase. To recover this dialkyl sulfate and at the same time provide the necessary cooling for the contactor, the hydrocarbon phase from settler 2 could be vaporized in the tube bundles of the contactor vessels 140 and 141. When the dipropyl sulfate hydrocarbon solution is fed to the tube bundle, the hydrocarbon will vaporize, leaving as a liquid, the dipropyl sulfate. This liquid will be carried through the tube bundle by the velocity of the liquid-vapor flow and may be sent to a separating vessel in the manner of trap or flash drum 62 wherein the vapors would be released from the liquid phase and such may be removed from the System. The liquid phase consisting of essentially pure dialkyl sulfate may then be pumped to the extraction zone or a later stage of the process.

However, this latter option, which is shown in a slightly different form in FIG. 2, is not necessarily optimum under certain conditions and does not particularly conserve propylene, if such occurs in particularly great excess. In the showing of FIG. 1b, the return of the overhead from the No. 2 settler 145 into the alkylation system via line 161 which is shown as joining the recycle line 86 from the trap 62, is optimal.

Isobutane for extraction of the diisopropyl sulfate from the alkylation section is supplied through line 122 from fractionation recycle line 114 from deisobutanizer 109. After passing heat exchange at 159, this line passes to rotating disc contactor 142 or other suitable countercurrent flow extraction vessel. The heavy phase from the No. 2 absorber settler, through line 155 and line 162 passes to the other end of the RDC. In the RDC, the heavy phase undergoes continuous countercurrent extraction with isobutane. The bulk of the dipropyl sulfate, some monopropyl sulfate and traces of water and conjunct polymers dissolve in the isobutane stream and form the extract which leaves the top of the extractor vessel 142 through line 163. The remainder of the heavy phase, comprised of any unextracted dipropyl sulfate, some monopropyl sulfate and the bulk of the Water and acid originally present in the alkylation acid leaves the bottom of the extractor through line 164 and is withdrawn from the unit as spent acid.

The extract from the previous step flows to the acid treater contactor 143 through line163 where it is brought into contact with a relatively minute amount of alkylation acid pumped from the No. 2 absorber feed stream through line 165. This acid picks up the traces of conjunct polymers dissolved in the extract. The reaction mix from acid treater contactor 143 ows via line 166 to settler 146 for phase separation and the treated extract from the settler 146 is returned to the strongest acid alkylation contactor for alkylation of the dipropyl sulfate and consequent strong acid release. This return is through line 167, joined by line 156 and entering line 161. The heavy phase from the acid treater settler 146 is recycle pumped through lines 168 and 169 by pump 170 for reextraction of any dipropyl sulfate picked up with the conjunct polymers.

yRefrigeration is required on both absorber contactors and on the isobutane chiller 159. The refrigerant operating temperature requirements are typically in the 20 F. range. This can be supplied by the vaporization of hydrocarbon from the fiash drum section of the effluent refrigeration system. Since the bulk of the refrigeration load is required for heat of reaction which normally is part of the total alkylation reaction head load, the total refrigeration duty is only slightly increased. Some shift in duty and some changes in vapor How rates are encountered.

High degree of extraction efliciency is necessary for maximum recovery of propyl sulfates. Whatever dipropyl sulfate is present in the raffinate from this step represents an acid loss from the process. This loss should be minimized. A rotating disc contactor as seen in Reman 2,601,674, issued June 24, 1952 entitled Liquid Contact Apparatus, etc. is here used as the extractor, operating with the hydrocarbon phase continuous. The extractor is designed to operate liquid full at a temperature the same as or slightly below the alkylation reactor temperature. Little or no heat is generated in the extractor, so temperature control may be effected by chilling the isobutane feed stream. The pressure in the extractor and the following acid treater system is allowed to float with the alkylation reactor pressure.

With respect to the acid treating step, the purpose is to scavange traces of conjunct polymeric compounds or acid oil from the extract with a small amount of alkylation acid. At the same time, efficient interfacial contact is required for the necessary degree of scavanging. A Stratco contactor is used for this step. The heat of solution generated in this step if so small compared to the volume of extract that no heat transfer surface is provided in the contactor. A slight subcooling in the extraction step may be employed to insure that the treated extract will leave the treater settler at essentially the alkylation reactor temperature.

The overhead line 156 from settler 145 has a valve thereon 156a. Prior to valve 156a, alternative No. 2 settler overhead takeoff line 300 may be employed. The latter has valve 301 and back pressure valve 302 thereon whereby the light phase overhead from settler 145 may be passed alternatively through valve controlled lines 303 and 304 to either acid treater 143 or lRDC 142.

In the systems contemplated in FIG. 1b, utilizing either overhead line 156 directly passing settler 145 overhead to the alkylation reaction zone or line 300 passing same to the RDC or acid treater, it is contemplated that both olefin and alkyl sulfate values in the settler 145 overhead will be conserved. These systems emphasize the maximum utilization of acid, but not particularly the total conversion of propylene by reaction with acid. Rather, the recovery of propylene by direct alkylation in the alkylation reaction step is visualized. Also in the system of FIG. 1b, it is contemplated that a relatively richer propylene or olefin feed addition to absorber 140 through line 147 will be utilized, rather than a leaner propylene mixture as would preferably be handled in the system of FIG. 2. Thus, in the arrangements or practices contemplated for this figure, there would not be such an excess of normal paraflinic hydrocarbons introduced to the alkylation system through line 147 as would require the vapor separation system to be described with respect to FIG. 2.

Referring to FIG. 2, therein is shown a modification of the system of FIG. lb wherein the manner of handling the effluent vapor overhead or light phase overhead from the No. 2 settler of the absorption system is varied to maximize the removal of normal parafiinic hydrocarbons from the absorption system. In this view, all of the vessels and flow lines which are essentially identical to the view of FIG. lb are numbered the same, but primed. This array, these diow lines and structures will not be redescribed in detail as the apparatus and functions are essentially the same. The `first difference to note in the FIG. 2 array lies in the fact that line 163 from the RDC, which previously ran to acid treater 143 runs directly into the line 161', returning to the alkylation reaction zone. As previously noted, `the acid treating step is optional. One of the main purposes of FIG. 2 is to illustrate how the extraction step effluent is handled in absence of the optional acid treating step. In a two-step absorption section as shown in FIG. 2, where there is little propylene overhead from settler 145 to be used in one of the manners seen in FIGS. lb and 3 (e.g., passage to acid treater), the acid treater step at 143 is less valuable and thus is less attractive. lt is necessary, in both the systems of FIGS. 1b and 2 and also in FIGS. 3 and 4 that at least certain portions of the overhead from the settler stage terminating the absorption section (through lines 156 and 156 in FIGS. 1b and 2) be retained in the system so that the sulfate values (as Well as any olefinic hydrocarbon in the overhead from settler 145 in the system of FIG. 1b) be retained in the system.

Likewise, the importance of processing the overhead from the settler 145 or 145' is seen in the use of the system shown in FIG. 2 wherein additional line 171 may be used to pass the No. 2 settler overhead through a heating stage as at 172 to flash vessel 173. The overhead from vessel 173, where there is a mere trace of propylene at the No. 2 settler in a two-stage absorption system as seen in FIGS. 1b and 2 comprises largely normal paraflins and same are removed from the system through line 174, thus lightening the load on the fractionation systems in the alkylation section. The bottoms from vessel 173 are passed through line 175 via pump 176 and line 177 directly to the alkylation system joining line 86 directly, if wished, or with line 161 in the manner of line 156'. Back pressure valve 174 holds the back pressure on the absorber system in the case where line 156 is not employed to handle any portion of the overhead from` settler 145. Valves 178 and 179 on lines 171 and 156', respectively, may control relative flow through these lines.

FIG. 2 illustrates the utility of a multi-stage absorption system in handling lean olefin (normal paraffin hydrocarbon rich) feed streams, said streams supplied through lines 147 to absorber 140. In such case, the normal parafinic hydrocarbon separation system utilizing line 171 for handling all or part of the absorption system light phase coming off settler 145 through line 156 is optimal. In this system, the maximum utilization of acid and essentially total conversion of propylene to alkyl sulfates in the absorption system is effected and the return to alkylation of the heavy phase from vessel 173 emphasizes conservation of dissolved sulfate values in the hydrocarbon overhead from settler 145 and the rejection through line 174 of normal paraflinic hydrocarbons prior to passage of sulfate values to alkylation.

In FIG. 3, therein is shown the optimal arrangement for a one-stage absorption system, where, necessarily, the absorption phase of the acid recovery system must be operated olefin-rich and there is a more considerable excess of olefin in the absorption settler overhead and a lesser percentage-wise production of dialkyl sulfates. In this case, it is very essential that the sulfate and olefin in the overhead from the absorber settler be conserved in the system. Absorber contactor 180 has driving motor 181 and header 182. Indirect heat exchange is provided of the contactor by line 18-3 which may come from the equivalent of trap 62 in FIG. la, with take-off therefrom to one side of the header through line 184 and return out of the header through line 185. Line 183 passes through heat exchange at 186 of the line 187 carrying the isobutane stream to the extraction step corresponding to line 122 of FIG. la. After heat exchange, line 183a joins line 185 and passes via line 188- back to the trap or flash drum corresponding to drum 62. The efuent from absorber 180 passes overhead through line 189 to settler 190. Bottoms from settler 190 are passed through line 191 and line 192 to the extraction vessel or rotating disc contactor 193 powered by driver 194. The alkylation acid is supplied from the acid settler through line 195 corresponding to line 137 in FIG. la. Pump 196 passes the alkylation acid through line 197 to the absorber contacter 180 and a slip stream through line 198 to the acid treater vessel 199. Propane propylene feed is supplied to absorber contactor through input line 200. The overhead or effluent from the acid treater 199 passes through line 201 to settler 202 with settler bottoms recycled through line 203, pump 204 and line 205 back to the RDC. Overhead from the settler 202 is passed back to the alkylation reactor through line 206.

The main improvement in the system of FIG. 3 lies in the 'use of the overhead line 207 from settler 190` to pass the settler overhead alternatively through lines 208 and 209 or divided there between` Yet otherwise, all or part of the settler 190 overhead may go into line 206 via line 207a. Line 208 connects the RDC intermediate the connections of lines 192 fand 187. Line 209 joins the effluent line 210 from the RDC, passing to the acid treater 199. In this manner, the propylene is maintained in contact with all acid values to maximize the quantity of alkyl sulfates produced and maintain the reaction in the direction of the dialkyl desired equilibrium. Likewise, the sulfate values in the settler overhead are conserved in the system and recycled to the alkylation from the settler 202 overhead through line 206.

FIG. 3 represents a single stage absorption system where a rich propylene (paraffin poor) feed through line 200 is hi-ghly recommended with the overhead from the absorption step containing a substantial percentage of olefin and a relatively direct passage of same to alkylation being desirable. This represents, in concert with FIG. 7, a simplest and cheapest arrangement of absorption apparatus featuring complete recovery of the excess olefins and also sulfate values in the light phase from the absorption step in alkylation and, by virtue of the driving force of the high olefin content in the absorption step, the best conditions for adequate acid utilization.

Referring to FIGS. 1b, 2 and 3, the back pressure valves seen in these figures on lines 156 and 207 and connecting lines thereto, serve to maintain the illustrated absorber sections or absorber contactors and associated settlers under such pressure that all flowing materials in the absorber section are maintained in liquid phase. While it is possible to produce alkyl sulfates in either liquid or vapor phase, liquid phase operation is much preferred for the maximum production of the dialkyl sulfate. As the liquid phase reaction, the absorption of propylene is quite rapid and relatively high yields are obtained in a relatively short time. In either phase, efficient contacting, relatively short reaction time and isothermal conditions are important for the latter. The vessels and apparatus systems of FIGS. 5-7 are necessarily operated under liquid phase conditions by virtue of the nature of their design. Other alternative equipment may be designed and employed for vapor phase operation.

Various olenic hydrocarbons or mixtures thereof may be employed in the alkylation reaction and absorption reaction zones. Most important in commercial alkylation for motor and aviation fuel are those olefins containing three to five carbon atoms. Olefins readily convertible to the dialkyl sulfates include the low molecular weight primary and secondary isomers with propylene optimal of these.

In the various preceding figures, several methods of conserving valuable materials in the absorption step light phase, such as excess olefin if present and alkyl sulfates dissolved in light hydrocarbons, have been described. FIGS. 1b land 3 show systems preferred when the absorber system olefin feed is olefin rich and a material presence of olefin in the absorber system light phase exists. Whether the absorption light phase goes directly to alkylation or passes thereto via the RDC (extractor section) or acid treater in whole or part, the olefin and alkyl sulfate values are conserved in the alkylation reaction zone in all cases. The presence of olefin from the absorber light phase in the RDC or acid treater affords the maximum exposure of acid values to olefin for reaction to dialkyl sulfates and, additionally, provides throughout the entire system a driving force to shift the reaction equilibrium toward dialkyl sulfate production. The system of FIG. 2 would not be preferred in the last described situations involving substantial presence of olefin in the absorber light phase. However, when essentially complete utilization of olefins is accomplished in the absorber step, the separation alternative via line 171 in FIG. 2 provides for rejection of paraftinic hydrocarbons prior to introduction to the alkylation zone. Any traces of unreacted olefin would be lost from the system. Sulfate values remain and pass to alkylation and are conserved therein. Should the line 147 feed vary in olen content, relative flow may be regulated by valves 178 and 179.

A prime necessity of any absorber system is to convert the maximum possible amount of acid to dialkyl sulfate. Dialkyl sulfates are highly soluble in isobutane in the extraction step and are recovered in same. Monoalkyl sulfates are only slightly soluble in isobutane of the extraction step, so a portion of same, only, is recovered in extraction, but most are discharged from the system with the raffinate. Likewise, the water and acid oil are discharged with the rafiinate. Because of this, the high dialkyl sulfate conversion is required in the system as the monoalkyl sulfate loss represents acid which could be recovered if the conversion to dialkyl sulfates were more efficient in the absorber system.

One way of achieving effective dialkyl sulfate conversion is to provide a high reaction driving force toward sulfate production by providing propylene excess in the absorber system over the quantity required to theoretically produce percent dialkyl sulfates from the quantity of acid made available in the absorber system. A second mode is to provide a plurality of reaction or contacting stages in the absorber step arranged in countercurrent relationship such that the used alkylation or lean acid contacts the olefin depleted hydrocarbon fed into the absorber stage and vice versa, that is, the richest acid stream in turn contacts the fresh or strongest olefin feed. Such a countercurrent system provides the maximum incremental driving force for any given olefin feed concentration. The maximum acid conversion to dialkyl sulfate would occur with a combination of the above described two factors. FIG. lb represents the latter option, FIG. 2 the second described and FIG. 3 one form of the first.

In a situation where the olefin containing hydrocarbon feed to the absorber step is olefin poor, it is highly desirable to reject the paraffinic hydrocarbons prior to alkylation. Such rejection will necessarily carry any olefin therewith which is present in the absorber light phase. The latter situation makes it optimal that all olefin be utilized in the absorption step. In this instance, the olefin reaction driving force being absent, a multistage countercurrent reaction system is necessary for adequate acid conversion. This is the case which would utilize the vaporization alternate in FIG. 2.

FIG. 5 illustrates a contacting device which provides in a single vessel, a countercurrent ow of acid and hydrocarbon feeds and incorporates or provides, by virtue of its design, multiple reaction stages or zones. Thus the incoming hydrocarbon with greatest propylene strength, as represented by line 147 meets, in the lowest reaction zone, the heavy phase which has been maximally converted to dipropyl sulfate. This heavy phase exits through line 155". At the opposite end of the reaction train, the used alkylation acid, representing the initial material to be converted, enters at line and, in the uppermost reaction zone, is contacted with the hydrocarbon most olefin depleted, which then leaves the reactor through line 156.

FIG. 5 gives the highest degree of acid conversion when the hydrocarbon feed through line 147 is olefin rich, in which case on can expect an excess of olefin in the absorption light phase coming off the vessel top at 156". Adequate acid conversion is possible in the FIG. showing when the hydrocarbon stream entering 147" is relatively lean in olefin, containing only suicient olefin values to stoichiometrically satisfy the dipropyl sulfate conversion of available acid. The presence of at least a trace of olefins in line 156" may be generally taken to indicate the successful conversion of a substantial proportion of the acid values to dialkyl sulfate, particularly where sufficient reaction stages have been provided. This latter remark is the case also with respect to affluent lines 156 and 156 of FIGS. 1b and 2.

Substitution of vessel 400 for the No. l and No, 2 absorber settlers (140, 141 and 144 and 145) of FIG. 1b would typically illustrate the above-described olefin rich case where lines 147, 150, 155 and 156 would substitute for the same double primed. Likewise, substitution of vessel 400 for the No. l and is withdrawn through fitting 406 would be carried by conventional level control means with reaction occurring therebelow.

This vessel, as illustrated, thus represents an adaptation of the vessel of Reman 2,601,674. The presence of vanes 413 provide somewhat intenser mixing, turbulence and contacting in the individual reaction zones defined between the stator rings 411. A further adaptation is the provision of indirect heat exchange means for the removal of the heat of reaction schematically indicated at 415. Feed to and from such cooling coils, the diameter of which is best seen in FIG. 6, may optionally and preferably involve feed and return lines 138 and 139 of FIG. la.

FIG. 7 is a single stage time tank arrangement serving an analogous function to the contactor-settler absorption system shown in FIG. 3. The cases where this system would be useful are defined with respect to FIG. 3 and the description thereof.

The absorption reaction is carried out primarily in the 4bafiied time tank 500. Phase contact is maintained by rapid circulation of the reaction mix by pump 501. Heat of reaction is removed by heat exchanger 502. A portion of the reaction mix is removed from the system via line 503, valve controlled at 504 and passing to separator 505. Line 207 from separator 50S carries the absorption light phase to the options contemplated in FIG. 3, while line 191 takes the heavy phase to extraction as in said figure. Alkylation acid is input through line 197' and olen containing hydrocarbon feed through line 200. The heat exchanging system may be linked in the manner of No. 2 settlers and absorbers (140', 141' .and 144' and 145') of FIG. 2 would typically illustrate the above-described olefin poor case where lines 147', 150', 155' and 156 would substitute for the same double primed.

Referring specifically to the structure of the vessel and incorporated parts therein of FIG. 5, the structure therein is identical with that of FIG. 1 of Reman 2,601,674, issued June 24, 1952 Liquid Contact Apparatus with Rotating Discs, with one exception. The latter comprises the provision of a plurality of vertical vanes on the rotating discs. The details of the Reman 2,601,674 patent will not be repeated but certain basic structure will be noted. Thus, the cylindrical vessel shell, vertically oriented, is capped at the top with perforated sheet 402 and closed at the bottom with perforated sheet 403. Inlet fittings 404 and 405 are provided adjacent the upper and lower extremities of the vessel, while outlet fittings 406 and 407 are additionally supplied. Suitable sealed bearing mounts 408 and 409 are provided to receive in rotation elongate shaft 410. The inner wall of the vessel has annular horizontal rings 411 subdividing the vessel into a vertical series of compartments, the height of which is determined by the vertical interval between rings 411. Shaft 410 carries a plurality of horizontal discs 412 having fixed to the upper surface there of plates or fianges 413. Suitable drive means are provided at the upper end of shaft 410 of conventional type, not to be described. Dotted line 414 at the top of vessel 400 indicates a typical level at which the light phase from the absorber section which FIG. 3 va lines 183 and 188', comparable t-o lines 183 and 188 in the previous figure. The output from time tank 500 passes via line 506 to pump 501, while the pump return to time tank 500 is via line 507.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the process.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in `the accompanying drawings is to be interpreted as illustrated and not in a limiting sense.

Having thus described my invention, I claim:

1. In an alkylation process where olefin-based alkylatable material comprising olefins and their mixtures is alkylated with isoparainic hydrocarbons in an alkylation reaction zone in the presence of alkylation sulphuric acid catalyst whereby to produce alkylate, the improvements which comprise:4

reacting van olefin containing hydrocarbon feed stream with used sulphuric acid catalyst which contains polymeric organic contaminants and water from said alkylation reaction zone to produce dialkyl sulfate in an absorption zone,

separating said reaction mixture within said absorption zone into a relatively lighter phase comprising a quantity of normal paraflinic hydrocarbons, olefinic hydrocarbons and dialkyl sulfates, and a relatively heavier phase comprising predominantly dialkyl sulfates, monoalkyl sulfates, acid, water and polymeric yorganic contaminants,

the quantity of dialkyl sulfates in said heavier phase being greater than the quantity of same within said lighter phase,

passing substantially all of the alkyl sulfates in said lighter phase and said relatively heavier phase ncluding all olefin in said relatively lighter phase to said alkylation reaction zone, and

passing said dialkyl sulphates in said relatively heavier phase to said alkylation reaction zone including extraction of dialkyl sulphates from the polymeric organic contaminants bef-ore returning same to said alkylation reaction zone.

2. A process as in claim 1 wherein relatively light hydrocarbons are employed to separate said sulfates into .an extract phase Aand a raffinate acid phase including acid soluble contaminants.

3. A process as in claim 1, including the step of separating the said relatively lighter phase itself into a light and a heavy phase, passing the former, comprising largely normal parainc hydrocarbons, out of system and the latter, comprising largely dialkyl sulfates, to said alkylation reaction zone.

4. A process as in claim 1 wherein the extracted dialkyl sulfates from the said relatively heavier phase are reacted with used alkylation acid, the latter reaction mix is separated into an acid-treated dialkyl sulfate phase and an acid phase, and said acid-treated dialkyl sulfate phase is passed to the alkylation reaction zone.

5. In a hydrocarbon conversion process wherein olefinbased alkylatable material comprising olefins, alkyl esters and their mixtures, is alkylated with isoparafnic hydrocarbons in an alkylation reaction zone in the presence of essentially sulfuric acid catalyst whereby to produce alkylate, the improvements which comprise:

passing a first hydrocarbon feed stream containing normal paraffnic and olenic hydrocarbons to a first absorption zone,

passing a second feed stream of sulfuric acid and predominantly alkyl esters, as well as water and acid soluble contaminants to said first absorption zone,

reacting said first and second feed streams in said first absorption zone under conditions of an excess of olefins whereby to create predominantly dialkyl sulfates in said first absorption zone,

passing as effluent from said first absorption zone a preponderance of alkylatable material comprising dialkyl sulfates, water, acid soluble contaminants, an excess of olelins and normal paraffinic hydrocarbons to a first separation zone,

separating as overhead from said first separation zone olefins and normal parafiinic hydrocarbons and dissolved alkyl esters therein and passing same as a first feed stream to a second absorption zone,

separating as bottoms from said first separation zone predominantly alkylatable material comprising dialkyl sulfates, water and acid soluble contaminants,

passing as a second feed stream to said second absorption zone a used acid catalyst stream from said alkylation zone comprising primarily sulfuric acid with water and acid soluble contaminants,

reacting said first and second feed streams in said second absorption zone to produce alkyl esters,

passing the effluent from the second absorption zone comprising normal paraffinic hydrocarbons, acid and alkyl esters to a second separation zone,

separating as overhead from said second separation zone a relatively lighter phase comprising a preponderance 'of normal hydrocarbons and a quantity of alkyl sulfates,

separating as bottoms from said second separation zone a relatively heavier phase material and passing same to said first absorption zone as a second feed stream thereto, and

passing the relatively lighter phase overhead from the second separation zone to the alkylation reaction zone.

6. In a hydrocarbon conversion process wherein olefin-based alkylatable material comprising olefins, alkyl esters and their mixtures, is alkylated with isoparafnic hydrocarbons in an alkylation reaction zone in the presence of essentially sulfuric acid catalyst whereby to produce alkylate, the improvements which comprise:

passing a first hydrocarbon feed stream containing normal paraffinic and olefinic hydrocarbons to a first absorption zone, passing a second feed stream of sulfuric acid Aand predominantly alkyl esters, as well as water and acid soluble contaminants to said first absorption zone, reacting said first and second feed streams in said first absorption zone under conditions of an excess of olefins whereby to create predominantly dialkyl sulfates in said first absorption zone, passing an efiiuent from said first absorption zone a preponderance of alkylatable material comprising dialkyl sulfates, water, acid soluble contaminants, an excess of olefins and normal parafiinic hydrocarbons to a rst separation zone, separating as overhead from said first separation zone olefins and normal parafiinic hydrocarbons and dissolved alkyl esters therein and passing same as a first feed stream to a second absorption zone, separating as bottoms from said first separation zone predominantly alkylatable material comprising dialkyl sulfates, water and acid soluble contaminants, passing as a second feed stream to said second absorption zone a used acid catalyst stream from said alkylation zone comprising primarily sulfuric acid with water and acid soluble contaminants, reacting said first and second feed streams n said second absorbing absorption zone to produce alkyl esters,

passing the effluent from the second absorption zone comprising normal parafiinic hydrocarbons, acid and alkyl esters to a second separation zone,

separating as overhead from said second separation zone a relatively lighter phase comprising a preponderance of normal hydrocarbons and a quantity of alkyl sulfates,

separating as bottoms from said second separation zone a relatively heavier phase material and passing same to said first absorption zone as a second feed stream thereto,

passing -the bottoms from said first separation zone to an extraction zone wherein light hydrocarbons are employed to separate said heavier phase into an extract phase comprising a solution of esters in said light hydrocarbons and a raffinate phase predominantly comprising acid soluble contaminants,

directly passing said extract phase to said alkylation reaction zone, and

passing the overhead from said second separation zone g to said alkylation reaction zone.

7. In a hydrocarbon conversion process wherein olefinbased alkylatable material comprising olefins, alkyl esters and their mixtures, is alkylated with isoparafiinic hydrocarbons in an alkylation reaction zone in the presence of essentially sulfuric acid catalyst whereby to produce alkylate, the improvements which comprise:

passing a first hydrocarbon feed stream containing normal paraffinic and olefinic hydrocarbons to a first absorption zone,

passing a second feed stream of sulfuric acid and predominantly alkyl esters, as well as water and acid soluble contaminants to said first absorption zone,

reacting said first and second feed streams in said first absorption zone under conditions of an excess of olefins whereby to create predominantly dialkyl sulfates in said first absorption zone,

passing as effluent from said first absorption zone a preponderance of alkylatable material comprising dialkyl sulfates, water, acid soluble contaminants, an

excess of olefins and normal parainic hydrocarbons to a first separation zone,

separating as overhead from said first separation zone oleiins and normal parafiinic hydrocarbons and dissolved alkyl esters therein and passing same as a first feed stream to a second absorption zone,

separating as bottoms from said first separation zone predominantly alkylatable material comprising dialkyl sulfates, water and acid soluble contaminants, passing as a second feed stream to said second absorption zone a used acid catalyst stream from said alkylation zone comprising primarily sulfuric acid with Water and acid soluble contaminants, reacting said first and second feed streams in said second absorption zone to produce alkyl esters, passing the efiluentvfrom the second absorption zone comprising normal parafiinic hydrocarbons, acid and alkyl esters to a second separation zone,

separating as overhead from said second separation zone a relatively lighter phase comprising a preponderance of normal hydrocarbons and a quantity of alkyl sulfates,

separating as bottoms from said second separation zone a relatively heavier phase material and passing same to said first absorption zone as a second feed stream thereto,

passing the bottoms from said first separation zone to an extraction zone wherein relatively light hydrocarbons are employed to separate said bottoms into an extract phase comprising a solution of esters in said light hydrocarbons and a rafiinate phase predominantly comprising acid soluble contaminants,

passing the extract phase to an acid treating zone,

19 wherein said extract is contacted with used alkylation acid,

passing the effluent from the acid treating zone, to a third separation zone where same is separated into a relatively lighter phase and a relatively heavier phase, and

passing the relatively lighter phase overhead therefrom to the alkylation reaction zone.

8. In a hydrocarbon conversion process wherein oleiinbased alkylatable material comprising olefins, alkyl esters and their mixtures, is alkylated with isoparafiinic hydrocarbons in an alkylation reaction zone in the presence of essentially sulfuric acid catalyst whereby to produce alkylate, the improvement which comprises:

passing a first feed hydrocarbon stream containing normal parafiinic and olefinic hydrocarbons to a first absorption zone, passing a second feed stream of sulfuric acid and predominantly alkyl esters, as well as water and acid soluble contaminants to said first absorption zone,

reacting said first and second feed streams in said first absorption zone under conditions of an excess of olefins whereby to create predominantly dialkyl sulfates in said first absorption zone,

passing as efiiuent from said first absorption zone a preponderance of alkylatable material comprising dialkyl sulfates, water, acid soluble oil contaminants, an excess of olefins and normal parainic hydrocarbons to a first separation zone,

separating as overhead from said first separation zone olefins and normal paraffinic hydrocarbons in preponderance and dissolved alkyl esters therein and passing same as a first feed stream to a second absorption zone,

separating as bottoms from said first separation zone predominantly alkylatable material comprising dialkyl sulfates with water and acid soluble contaminants,

passing as a second feed stream to said second absorption zone a used acid catalyst stream from said alkylation zone comprising primarily sulfuric acid with water and acid soluble contaminants,

reacting said first and second feed streams in said second absorption zone under conditions of an excess of olefin to produce alkyl esters,

passing the efiiuent from the second absorption zone to a second separation zone comprising normal parafnic hydrocarbons, an excess of olenic hydrocarbons, acid and alkyl esters,

separating as overhead from said second separation Zone a relatively lighter phase comprising a preponderance of normal parafiinic hydrocarbons, a trace at least of olelinic hydrocarbons and a quantity of alkyl sulfates, and

separating as bottoms from said second separation zone a relatively heavier phase material and passing same to said first absorption zone as a second feed stream thereto.

References Cited UNITED STATES PATENTS 2,361,465 10/1944 Filbert 260-683.61 3,227,774 1/1966 Goldsby 260-683-61 3,227,775 1/1966 Goldsby 260-683.61 3,234,301 l/1966 Goldsby 260-683.62 2,370,771 3/1945 Bowerman 260-683.61 2,381,041 8/1945 de Jong 260-683.61

DELBERT E. GANTZ, Primary Examiner.

G. I. CRASANAKIS, Assistant Examiner.

U.S. Cl. X.R. 

